Adhesive and method of encapsulating organic electronic device using the same

ABSTRACT

An adhesive, and an encapsulated product and method of encapsulating an organic electronic device (OED) using the same are provided. The adhesive film serves to encapsulate the OED and includes a curable resin and a moisture absorbent, and the adhesive includes a first region coming in contact with the OED upon encapsulation of the OED and a second region not coming in contact with the OED. Also, the moisture absorbent is present at contents of 0 to 20% and 80 to 100% in the first and second regions, respectively, based on the total weight of the moisture absorbent in the adhesive.

This application is continuation application of U.S. patent applicationSer. No. 14/740,006, filed Jun. 15, 2015, which is a Continuation ofU.S. patent application Ser. No. 14/289,212, filed May 28, 2014, nowU.S. Pat. No. 9,105,648, which is a Continuation of U.S. patentapplication Ser. No. 13/886,098 filed May 2, 2013, now U.S. Pat. No.8,742,411 which is a Continuation Bypass of International ApplicationNo. PCT/KR2011/008280, filed Nov. 2, 2011, and claims the benefit ofKorean Application Nos. 10-2010-0108113 filed on Nov. 2, 2010,10-2011-0004054 filed on Jan. 14, 2011, and 10-2011-0113121 filed onNov. 2, 2011, the contents of which are incorporated by reference intheir entirety for all purposes as if fully set forth below.

BACKGROUND 1. Field of the Invention

The present invention relates to an adhesive and a method ofencapsulating an organic electronic device (OED) using the same.

2. Discussion of Related Art

An organic electronic device (OED) refers to a device including anorganic material layer that generates an alternating current withelectric charges through the combination of holes and electrons, andexamples of the OED may include a photovoltaic device, a rectifier, atransmitter and an organic light emitting diode (OLED).

Among the OEDs, the OLED has low power consumption and rapid responsetime and is desirable in manufacturing a thin display or lightingdevice, compared to a conventional light source. Also, the OLED isexpected to be applied to various fields such as a variety of portabledevices, monitors, notebook computers and televisions due to itsexcellent space accessibility.

Durability is one of the most important problems to be solved in orderto commercialize an OLED and expand its use. An organic material andmetal electrode included in the OLED are easily oxidized by externalfactors such as moisture. Thus, a product including the OLED is highlysensitive to environmental factors. Accordingly, a variety of methodshave been proposed to effectively prevent oxygen or moisture frompenetrating into an OED such as an OLED from the external environments.

A method of processing a metal can or a glass into a cap shape having agroove and loading the groove with a powdery dehumidifying agent toabsorb moisture or manufacturing a metal can or a glass in the form of afilm and sealing the film using a double-sided adhesive tape has beenused in the art.

Japanese Patent Laid-Open Publication No. Hei9-148066 discloses anorganic EL element including a stacked body having a structure in whichan organic light emitting layer made of an organic compound is arrangedbetween a pair of facing electrodes, an airtight container configured toprotect the stacked body from the air, and a drying unit such as analkaline metal oxide or an alkaline earth metal oxide arranged in theairtight container. However, such an organic EL element has problems inthat the entire thickness of a display device is increased due to ashape of the airtight container, it is vulnerable to physical impactsdue to the presence of the internal space, and its heat radiationproperty is poor when it is manufactured on a large scale.

U.S. Pat. No. 6,226,890 discloses a method of desiccating an electronicdevice including a desiccant layer formed using a desiccant and abinder, wherein the desiccant includes solid particle having a particlesize of 0.1 to 200 μm. However, the desiccant layer has insufficientmoisture absorption capacity. When a curable resin in a cured state doesnot meet a water vapor transmission rate (WVTR) of 50 g/m²·day or lessdue to the characteristics of the binder surrounding a moistureabsorbent, the curable resin does not exert sufficient performancebecause its moisture apposition rate actually increases during anacceleration test.

In order to solve these problems, Korean Patent Publication No.2007-0072400 discloses an organic EL element. When an epoxy sealantincludes a moisture absorbent, the epoxy sealant serves to chemicallyabsorb moisture passed into the organic EL element and slow moisturepenetration into the organic EL element. However, physical damage may becaused to the organic EL element due to volume expansion caused byreaction of the moisture absorbent with moisture. Also, when a metaloxide is used as the moisture absorbent, the metal oxide may react withmoisture to generate a strongly basic substance, which causes chemicaldamage to a passivation layer and a cathode layer.

Therefore, there is a demand for development of an encapsulationmaterial capable of effectively preventing penetration of moisture andalso reducing damage to an OED.

SUMMARY OF THE INVENTION

The present invention is directed to an adhesive, and a product andmethod of encapsulating an organic electronic device (OED) using anadhesive.

One aspect of the present invention provides an adhesive forencapsulating an OED. Here, the adhesive includes a curable resin andmoisture absorbent, the adhesive includes a first region coming incontact with the OED upon encapsulation of the OED, and a second regionnot coming in contact with the OED, and the moisture absorbent ispresent at contents of 0 to 20% and 80 to 100% in the first and secondregions, respectively, based on the total weight of the moistureabsorbent in the adhesive.

Another aspect of the present invention provides an encapsulated OEDproduct including a substrate, an OED formed on the substrate and anadhesive for encapsulating the OED. Here, the first region of theadhesive covers the OED.

Still another aspect of the present invention provides a method ofencapsulating an OED. Here, the method includes applying the adhesive toa substrate having the OED formed thereon so that the first region ofthe adhesive may cover the OED and curing the adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent to those of ordinary skill in theart by describing in detail exemplary embodiments thereof with referenceto the attached drawings, in which:

FIGS. 1 to 3 are cross-sectional views showing an adhesive filmaccording to one exemplary embodiment of the present invention.

FIGS. 4 and 5 are cross-sectional views showing an encapsulated OEDproduct according to one exemplary embodiment of the present invention.

FIG. 6 shows the Fourier transform infrared (FT-IR) analysis results ofan adhesive film manufactured in Example 1.

FIG. 7 shows the FT-IR analysis results of an adhesive film manufacturedin Comparative Example 2.

DESCRIPTION OF REFERENCE NUMERALS

11: base film or release film

12: adhesive

14: cover film (base film or release film)

21: substrate

22: adhesive

12 a: first region, 12 b: second region

13, 23: moisture absorbent

24: cover substrate

25: organic electronic device

26: passivation film

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail. However, the present invention is not limited tothe embodiments disclosed below, but can be implemented in variousforms. The following embodiments are described in order to enable thoseof ordinary skill in the art to embody and practice the presentinvention.

Although the terms first, second, etc. may be used to describe variouselements, these elements are not limited by these terms. These terms areonly used to distinguish one element from another. For example, a firstelement could be termed a second element, and, similarly, a secondelement could be termed a first element, without departing from thescope of exemplary embodiments. The term “and/or” includes any and allcombinations of one or more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exemplaryembodiments. The singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” and/or “including,” when used herein, specifythe presence of stated features, integers, steps, operations, elements,components and/or groups thereof, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

With reference to the appended drawings, exemplary embodiments of thepresent invention will be described in detail below. To aid inunderstanding the present invention, like numbers refer to like elementsthroughout the description of the figures, and the description of thesame elements will be not reiterated.

An adhesive according to one exemplary embodiment of the presentinvention serves to encapsulate an organic electronic device (OED), theadhesive having a multilayer structure. The adhesive according to thepresent invention may cover the entire surface of the organic electronicdevice (OED).

More particularly, the adhesive includes a curable resin and a moistureabsorbent. Further, the adhesive includes a first region coming incontact with the OED upon encapsulation of the OED and a second regionnot coming in contact with the OED, and the moisture absorbent ispresent at contents of 0 to 20% and 80 to 100% in the first and secondregions, respectively, based on the total weight of the moistureabsorbent in the adhesive. The adhesive according to the presentinvention may be a curable hot-melt adhesive.

Throughout the specification, the term “organic electronic device (OED)”refers to a product or device having a structure including an organiclayer which generates an alternating current with electric chargesthrough the combination of holes and electrons between a pair of facingelectrodes, and examples of the OED may include a photovoltaic device, arectifier, a transmitter and an organic light emitting diode (OLED), butthe present invention is not limited thereto. According to one exemplaryembodiment of the present invention, the OED may be an OLED.

Throughout the specification, the term “hot-melt adhesive” refers to akind of an adhesive that may maintain a solid or semi-solid phase atroom temperature, attach a plate without bubbles due to flowabilityexerted when heat is applied, and strongly fix a subject using anadhesive when a curing reaction is completed. The adhesive according tothe present invention may have a viscosity at room temperature of 10⁶dyne·s/cm² or more, and preferably 10⁷ dyne·s/cm² or more. The term“room temperature” refers to a temperature at which an adhesive is notheated or cooled, for example, a temperature of approximately 15° C. to35° C., more particularly approximately 20° C. to 25° C., and furtherparticularly approximately 25° C. The viscosity may be measured using anadvanced rheometric expansion system (ARES). According to the presentinvention, it is possible to facilitate processability in operations andencapsulate a plate with a uniform thickness during encapsulation of anOED by regulating the viscosity of a hot-melt adhesive within thisviscosity range. Also, problems such as contraction and volatile gasgeneration which may be caused by curing of a resin may be remarkablyreduced to prevent the physical or chemical damage to an organicelectronic device. According to the present invention, as long as anadhesive is maintained in a solid or semi-solid phase at roomtemperature, an upper limit of the viscosity is not particularlylimited. For example, the viscosity may be controlled to a range ofapproximately 10⁹ dyne·s/cm² or less in consideration of theprocessability.

Unlike the conventional techniques, according to exemplary embodimentsof the present invention, the adhesive for encapsulating an OED has amultilayer structure, which includes a curable resin and moistureabsorbent, and the adhesive further includes a first region coming incontact with the OED upon encapsulation of the OED, and a second regionnot coming in contact with the OED. Also, the moisture absorbent may bepresent at contents of 0 to 20% and 80 to 100% in the first and secondregions, respectively, based on the total weight of the moistureabsorbent in the adhesive. When the content of the moisture absorbent inthe first region closer to the OED exceeds 20%, the volume expansioncaused by reaction of the moisture absorbent with moisture may not becontrolled using only a curing resin, which leads to increased cracks ina film of the OED.

The physical and chemical damage to the OED due to the presence of themoisture absorbent in the adhesive used as an encapsulation material maybe prevented by controlling the content of the moisture absorbent in theadhesive having such a multilayer structure and the first and secondregions. Any method of forming an adhesive having a multilayer structureknown in the art may be used without limitation as long as the methodcan divide the adhesive into first and second regions so that the firstand second regions can have a multilayer structure.

Except for the content of the moisture absorbent, the first and secondregions of the adhesive may have the same or different kinds andcontents of the other components, for example, a curable resin, amoisture absorbent, other additives, or a filler. Unless definedotherwise herein, the following description is related to both the firstand second regions of the adhesive.

The curable resin in a cured state may have a water vapor transmissionrate (WVTR) of 50 g/m²·day or less, preferably 30 g/m²·day or less, morepreferably 20 g/m²·day or less, and most preferably 15 g/m²·day or less.The term “cured state of a curable resin” refers to a state in which acurable resin may be cured or cross-linked alone or by reaction withanother component such as a curing agent so that the curable resin canmaintain constant contents of a moisture absorbent and a filler andserve as a structural adhesive when the curable resin is used as anencapsulation material. According to the present invention, the WVTRrefers to a WVTR of a cured product which is measured at 38° C. and 100%relative humidity (R.H.) in a transverse direction when the curedproduct is formed by curing a curable resin and then processed into afilm having a thickness of 80 μm. Also, the WVTR is measured accordingto the ASTM F1249 standard.

The WVTR may be controlled to effectively prevent penetration ofmoisture, humidity or oxygen into a product for encapsulating an OED(hereinafter referred to as an “OED-encapsulating product”) andeffectively introduce a moisture-reactive absorbent into theOED-encapsulating product.

According to the present invention, as the WVTR of a resin in a curedstate is decreased, an encapsulation structure of the resin shows moreexcellent performance Therefore, a lower limit of the WVTR is notparticularly limited.

Specific kinds of the curable resin that may be used herein may, forexample, include a variety of thermosetting or photocurable resins knownin the art, but the present invention is not particularly limitedthereto. The term “thermosetting resin” refers to a resin that may becured by proper application of heat or through an aging process, and theterm “photocurable resin” refers to a resin that may be cured byirradiation with electromagnetic waves. Also, a category of theelectromagnetic waves described above may include a particle beam suchas an α-particle beam, a proton beam, a neutron beam and an electronbeam as well as microwaves, infrared rays (IR), ultraviolet rays (UV),X-rays and γ-rays. According to the present invention, one example ofthe photocurable resin may be a cation-photocurable resin. Thecation-photocurable resin refers to a resin that may be cured by acation polymerization or cation curing reaction induced by irradiationwith electromagnetic waves. Also, the curable resin may be a dualcurable resin showing both of the thermosetting and photocurablecharacteristics.

According to the present invention, specific kinds of the curable resinare not particularly limited as long as they have the above-describedcharacteristics. For example, the curable resin that may be cured togive an adhesive property may include resins that contain at least onefunctional group which can be cured by heat, such as a glycidyl group,an isocyanate group, a hydroxyl group, a carboxyl group or an amidegroup, or contain at least one functional group which can be cured byirradiation with electromagnetic waves, such as an epoxide group, acyclic ether group, a sulfide group, an acetal group or a lactone group.In addition, specific kinds of such a resin may include an acryl resin,a polyester resin, an isocyanate resin or an epoxy resin, but thepresent invention is not limited thereto.

According to the present invention, an aromatic or aliphatic epoxy resinor a linear or branched epoxy resin may be used as the curable resin.According to one exemplary embodiment of the present invention, an epoxyresin having an epoxy equivalent weight of 180 g/eq to 1,000 g/eq may beused as the epoxy resin containing at least two functional groups. Theepoxy resin having the above-described epoxy equivalent weight range maybe used to effectively maintain the characteristics such as adhesion andglass transition temperature of a cured product. Examples of such anepoxy resin may include a cresol novolac epoxy resin, a bisphenol A-typeepoxy resin, a bisphenol A-type novolac epoxy resin, a phenol novolacepoxy resin, a tetrafunctional epoxy resin, a biphenyl-type epoxy resin,a triphenolmethane-type epoxy resin, an alkyl-modified triphenolmethaneepoxy resin, a naphthalene-type epoxy resin, a dicyclopentadiene-typeepoxy resin or a dicyclopentadiene-modified phenol-type epoxy resin,which may be used alone or in combination.

According to the present invention, an epoxy resin having a ringstructure in the molecular structure may be preferably used, and anepoxy resin containing an aromatic group (for example, a phenyl group)may be more preferably used herein. When the epoxy resin contains anaromatic group, a cured product of the epoxy resin has excellent thermaland chemical stabilities and also shows low moisture absorption, whichleads to improved reliability of an encapsulation structure of the OED.Specific examples of the aromatic group-containing epoxy resin that maybe used herein may include, but are not limited to, a biphenyl-typeepoxy resin, a dicyclopentadiene-type epoxy resin, a naphthalene-typeepoxy resin, a dicyclopentadiene-modified phenol-type epoxy resin, acresol-based epoxy resin, a bisphenol-based epoxy resin, a xyloxy-basedepoxy resin, a multifunctional epoxy resin, a phenol novolac epoxyresin, a triphenolmethane-type epoxy resin and an alkyl-modifiedtriphenolmethane epoxy resin, which may be used alone or in combination.

According to the present invention, a silane-modified epoxy resin havinga silane-modified epoxy resin, preferably an aromatic group, may be morepreferably used as the epoxy resin. When the epoxy resin is structurallymodified with silane so that it can have a silane group, it is possibleto maximize an adhesive property to materials for a glass substrate orinorganic substrate of the OED and also improve properties such as amoisture barrier property, durability and reliability. Specific kinds ofsuch an epoxy resin that may be used herein are not particularlylimited, and the epoxy resin may be, for example, easily purchased froma manufacturer such as

The adhesive according to the present invention includes a moistureabsorbent in addition to the curable resin. The term “moistureabsorbent” refers to a general component that can absorb or removemoisture or humidity, which is flowing in from the outside, by physicalor chemical reaction. That is, the moisture absorbent means amoisture-reactive absorbent or physical absorbent, and a mixture thereofmay also be used herein.

The moisture-reactive absorbent serves to absorb moisture or humidity bychemical reaction with humidity, moisture or oxygen introduced into anadhesive. The physical absorbent may suppress moisture or humidity frompenetrating into an encapsulation structure by increasing a travel pathof the moisture or humidity and maximize a barrier property to moistureand humidity by interaction with a matrix structure of the curable resinand a moisture-reactive absorbent.

According to one exemplary embodiment of the present invention, in orderto avoid damage to the OED, the moisture absorbent may include a smallamount of the moisture-reactive absorbent in the first region of theadhesive.

Specific kinds of the moisture absorbent that may be used herein are notparticularly limited. For example, the moisture-reactive absorbent mayinclude a metal powder, a metal oxide (e.g., alumina), a metal salt,phosphorus pentoxide (P₂O₅), or a mixture thereof, and the physicalabsorbent may include silica, zeolite, titania, zirconia ormontmorillonite.

Specific examples of the metal oxide described above may include lithiumoxide (Li₂O), sodium oxide (Na₂O), barium oxide (BaO), calcium oxide(CaO) or magnesium oxide (MgO), and examples of the metal salt mayinclude, but are not limited to, a sulfate such as lithium sulfate(Li₂SO₄), sodium sulfate (Na₂SO₄), calcium sulfate (CaSO₄), magnesiumsulfate (MgSO₄), cobalt sulfate (CoSO₄), gallium sulfate (Ga₂(SO₄)₃),titanium sulfate (Ti(SO₄)₂) or nickel sulfate (NiSO₄); a metal halidesuch as calcium chloride (CaCl₂), magnesium chloride (MgCl₂), strontiumchloride (SrCl₂), yttrium chloride (YCl₃), copper chloride (CuCl₂),cesium fluoride (CsF), tantalum fluoride (TaF₅), niobium fluoride(NbF₅), lithium bromide (LiBr), calcium bromide (CaBr₂), cesium bromide(CeBr₃), selenium bromide (SeBr₄), vanadium bromide (VBr₃), magnesiumbromide (MgBr₂), barium iodide (BaI₂) or magnesium iodide (MgI₂); or ametal chlorate such as barium perchlorate (Ba(ClO₄)₂) or magnesiumperchlorate (Mg(ClO₄)₂).

According to the present invention, the moisture absorbent such as ametal oxide may be properly processed and blended with a composition.For example, the adhesive may be a thin film having a thickness of 30 μmor less according to the kind of the OED to which an adhesive isapplied. In this case, a process of grinding a moisture absorbent isrequired. The grinding of the moisture absorbent may be performed usinga process such as 3-roll milling, bead milling or ball milling. Also,when the adhesive of the present invention is used in top emission-typeOEDs, the permeability of the adhesive itself is very important, andthus the moisture absorbent should be decreased in size. Thus, thegrinding process may be required in such applications.

The second region of the adhesive according to the present invention mayinclude the moisture absorbent at a content of 1 part by weight to 100parts by weight, preferably 5 parts by weight to 50 parts by weight,based on 100 parts by weight of the curable resin. When the content ofthe moisture absorbent is controlled to more than 5 parts by weight, acured product may show an excellent barrier property to moisture andhumidity. In addition, when the content of the moisture absorbent iscontrolled to less than 50 parts by weight, a cured product may show anexcellent barrier property to moisture when forming an encapsulationstructure of a thin film.

Unless defined otherwise herein, the unit “parts by weight” refers to aweight ratio of each component.

Accordingly, the first region of the adhesive according to the presentinvention may also include the moisture absorbent at a content of 0parts by weight to 20 parts by weight, based on 100 parts by weight ofthe curable resin. When the content of the moisture absorbent is 0 partsby weight, the moisture absorbent is not present in the first region ofthe adhesive, but is present only in the second region. When the contentof the moisture absorbent is controlled to 20 parts by weight or less,it is possible to maximize a barrier property to moisture and alsominimize physical and chemical damage to the OED caused by the presenceof the moisture absorbent.

The adhesive according to the present invention may include a filler,preferably an inorganic filler. The filler may suppress moisture orhumidity from penetrating into an encapsulation structure by increasinga travel path of the moisture or humidity, and maximize a barrierproperty to moisture and humidity by interaction with a matrix structureof the curable resin and a moisture-reactive absorbent. Specific kindsof the filler that may be used herein are not particularly limited. Forexample, clay, talc, acicular silica, or a mixture of at least onethereof may be used alone or in combination.

According to the present invention, in order to improve the efficiencyof binding between a filler and an organic binder, a productsurface-treated with an organic material may be used as the filler, ormay also be used together with a coupling agent.

The adhesive according to the present invention may include the fillerat a content of 1 part by weight to 50 parts by weight, preferably 1part by weight to 20 parts by weight, based on 100 parts by weight ofthe curable resin. When the content of the filler is controlled to 1part by weight or more, a cured product having an excellent barrierproperty to moisture or humidity and excellent mechanical properties maybe provided. Also, when the content of the filler is controlled to 50parts by weight or less according to the present invention, the curableresin may be prepared in the form of a film, and a cured product showingan excellent barrier property to moisture or humidity even when thecurable resin is formed into a thin film may also be provided.

The adhesive according to the present invention may further include acuring agent which can react with a curable resin to form a matrix suchas a cross-linking structure.

Specific kinds of the curing agent that may be used herein are notparticularly limited, but may be properly selected according to thecurable resins used, or the kinds of functional groups included in thecurable resins. According to the present invention, for example, when anepoxy resin is used as the curable resin, a typical curing agent forepoxy resins known in the art may be used as the curing agent. Moreparticularly, the curing agent may include, but is not limited to,various compounds such as an amine-based compound, an imidazole-basedcompound, a phenol-based compound, a phosphorus-based compound or anacid anhydride-based compound, which may be used alone or incombination.

The adhesive according to the present invention may, for example,include the curing agent at a content of 1 part by weight to 20 parts byweight, preferably 1 part by weight to 10 parts by weight, based on 100parts by weight of the thermosetting resin. However, the content of thethermosetting resin is merely one exemplary embodiment of the presentinvention. That is, the content of the curing agent may be varied in thepresent invention according to the kind and content of the curableresins or their functional groups, the matrix structure to be realized,or the cross-linking density.

The adhesive according to the present invention may further include ahigh molecular weight resin. The high molecular weight resin may serveto improve formability when a composition according to the presentinvention is shaped in the form of a film or sheet. Also, the highmolecular weight resin may serve as a high-temperature viscositycontrolling agent for controlling the flowability during a hot-meltingprocess.

Kinds of the high molecular weight resin that may be used herein are notparticularly limited as long as they have compatibility with othercomponents such as a curable resin. Specific examples of the highmolecular weight resin that may be used herein may include, but are notlimited to, resins having a weight average molecular weight of 20,000 ormore, for example, a phenoxy resin, an acrylate resin, a high molecularweight epoxy resin, a super-high molecular weight epoxy resin, ahigh-polarity functional group-containing rubber and a high-polarityfunctional group-containing reactive rubber, which may be used alone orin combination.

When the high molecular weight resin is included in the adhesiveaccording to the present invention, the content of the high molecularweight resin is controlled according to the desired physical properties,but the present invention is not particularly limited thereto. Forexample, according to the present invention, the high molecular weightresin may be included at a content of approximately 200 parts by weightor less, preferably 150 parts by weight or less, and more preferablyapproximately 100 parts by weight or less, based on 100 parts by weightof the curable resin. According to the present invention, when thecontent of the high molecular weight resin is controlled to 200 parts byweight or less, the high molecular weight may effectively maintain thecompatibility with each component of a resin composition, and alsofunction as an adhesive.

Also, the adhesive according to the present invention may furtherinclude an additional additive such as a filler for improving thedurability of a cured product, a coupling agent for improving themechanical and adhesive strengths, a UV stabilizer and an antioxidant,without departing from the scope of the present invention.

Another exemplary embodiment of the present invention is directed to anadhesive film. A structure of the adhesive film according to the presentinvention is not particularly limited as long as the structure of theadhesive film includes the adhesive including the first and secondregions as described above. For example, the adhesive film according tothe present invention may have a structure including a base film orrelease film (hereinafter referred to as a “first film”); and anadhesive formed on the base film or release film.

Also, the adhesive film according to the present invention may furtherinclude a base film or release film (hereinafter referred to as a“second film”) formed on the adhesive.

FIGS. 1 to 3 are cross-sectional views showing an adhesive filmaccording to one exemplary embodiment of the present invention.

As shown in FIGS. 1 and 2, the adhesive film according to the presentinvention may include an adhesive 12 formed on a base film or releasefilm 11. FIG. 1 shows that a moisture absorbent is present only in asecond region of an adhesive according to the present invention, andFIG. 2 shows that a small amount of a moisture absorbent is also presentin a first region.

According to another exemplary embodiment of the present invention, theadhesive film according to the present invention may further include abase film or release film 14 formed on the adhesive 12, as shown in FIG.3. However, the adhesive film as shown in FIG. 3 is merely one exemplaryembodiment of the present invention, and a stacking sequence of thefirst and second regions of the adhesive may be reversed, whennecessary.

Specific kinds of the first film that may be used herein are notparticularly limited. According to the present invention, a typicalpolymer film known in the art may, for example, be used as the firstfilm. According to the present invention, the base film or release filmthat may be used herein may, for example, include a polyethyleneterephthalate film, a polytetrafluoroethylene film, a polyethylene film,a polypropylene film, a polybutene film, a polybutadiene film, a vinylchloride copolymer film, a polyurethane film, an ethylene-vinyl acetatefilm, an ethylene-propylene copolymer film, an ethylene-acrylic acidethyl copolymer film, an ethylene-acrylic acid methyl copolymer film ora polyimide film. Also, one or both surfaces of the base film or releasefilm according to the present invention may be subjected to adequaterelease treatment. Examples of a release agent used to release a basefilm may include an alkyd-based release agent, a silicone-based releaseagent, a fluorine-based release agent, an unsaturated ester-basedrelease agent, a polyolefin-based release agent or a wax-based releaseagent. Among these, an alkyd-based, silicone-based or fluorine-basedrelease agent may be preferably used in an aspect of heat resistance,but the present invention is not limited thereto.

Also, the kinds of second film (hereinafter also referred to as a “coverfilm”) that may be used herein are not particularly limited. Forexample, according to the present invention, the same or different kindof the first film may be used as the second film when a range of thesecond film falls within the above-described range of the first film.According to the present invention, the second film may also besubjected to release treatment, and used.

According to the present invention, the thickness of such a base film orrelease film (a first film) is not particularly limited, and may beproperly selected according to applications. According to the presentinvention, the thickness of the first film may be, for example, in arange of 10 μm to 500 μm, preferably 20 μm to 200 μm. When the thicknessof the first film is less than 10 μm, a base film may be easily deformedduring a manufacturing process, whereas an economical efficiency may bedegraded when the thickness of the first film exceeds 500 μm.

According to the present invention, the thickness of the second film isnot particularly limited. According to the present invention, thethickness of the second film may be, for example, set to the samethickness as the first film. According to the present invention, thethickness of the second film may also be set to a relatively smallerthickness than the first film in consideration of the processability.

The thickness of the adhesive included in the adhesive film according tothe present invention is not particularly limited, but may be properlyselected according to the following conditions in consideration ofapplications of the adhesive film. However, the first region of theadhesive preferably has a smaller thickness than the second region. Forthe adhesive included in the adhesive film according to the presentinvention, for example, the first region of the adhesive may have athickness of 1 μm to 20 μm, preferably 2 μm to 15 μm. When the thicknessof the first region is less than 1 μm, the ability of the second regionof the adhesive to protect the OED from damage factors may be degraded,for example, even when the adhesive film is used as an encapsulationmaterial for OEDs. When the thickness of the first region exceeds 20 μm,the ability of the second region of the adhesive to prevent penetrationof moisture may be degraded. The second region of the adhesive may havea thickness of 5 μm to 200 μm, preferably 5 μm to 100 μm. When thethickness of the second region is less than 5 μm, the ability to preventpenetration of moisture may be insufficient. When the thickness of thesecond region exceeds 200 μm, it is difficult to secure theprocessability, damage may be caused to a deposited film of an organicEL element as the expansion in thickness is increased due to thereactivity with moisture, and the economical efficiency may be degraded.

According to the present invention, a method of manufacturing such anadhesive film is not particularly limited. For example, each of thefirst and second regions of the adhesive may be prepared using a methodincluding a first operation of coating a base film or release film witha coating solution including a composition of the above-describedadhesive; and a second operation of drying the coating solution coatedin the first operation.

Also, a method of stacking each of the first and second regions is notparticularly limited. For example, an adhesive film having a multilayerstructure may be formed by joining first and second regions formedrespectively on separate release films to each other, and a secondregion may be directly formed on a first region, or vice versa.

Also, the method of manufacturing an adhesive film according to thepresent invention may further include a third operation of furthercompressing the base film or release film onto the coating solutiondried in the second operation.

The first operation according to the present invention is to prepare acoating solution by dissolving or dispersing the above-describedcomposition of the adhesive in a proper solvent. In this procedure, thecontent of the epoxy resin included in the coating solution may beproperly controlled according to the desired properties such as abarrier property to moisture and film formability.

According to the present invention, kinds of the solvent used inpreparation of the coating solution are not particularly limited.However, when a drying time of the solvent is too long, or the solventis dried at a high temperature, the workability or the durability of theadhesive may be deteriorated. Therefore, the use of a solvent having anevaporation temperature of 100° C. or lower is preferred. According tothe present invention, a small amount of the solvent having anevaporation temperature greater than this temperature range may be usedin consideration of the film formability. Examples of the solvent thatmay be used herein may include, but are not limited to,methylethylketone (MEK), acetone, toluene, dimethylformamide (DMF),methylcellosolve (MCS), tetrahydrofuran (THF) or N-methylpyrrolidone(NMP), which may be used alone or in combination.

In the first operation of the present invention, a method of coating abase film or release film with such a coating solution is notparticularly limited. For example, a known method such as knife coating,roll coating, spray coating, gravure coating, curtain coating, commacoating or lip coating may be used without limitation.

The second operation of the present invention is to form an adhesive bydrying the coating solution coated in the first operation. That is, inthe second operation of the present invention, an adhesive may be formedby heating the coating solution coated on the film to dry the film andremove the solvent. In this case, the drying conditions are notparticularly limited. For example, the drying process may be performedat a temperature of 70° C. to 200° C. for 1 to 10 minutes.

In the method of manufacturing an adhesive film according to the presentinvention, a third operation of compressing an additional base film orrelease film onto the adhesive formed on the film may be furtherperformed after the second operation.

Such a third operation of the present invention may be performed bycompressing an additional release film or base film (a cover film orsecond film) onto the dried adhesive after coating the film using ahot-roll lamination or press process. In this case, the third operationmay be performed using a hot-roll lamination process in aspects of theprobability and efficiency of a continuous process. In this case, theprocess may be performed at a temperature of approximately 10° C. to100° C. and a pressure of approximately 0.1 kgf/cm² to 10 kgf/cm².

Another exemplary embodiment of the present invention is directed toproviding an encapsulated OED product including a substrate, an OEDformed on the substrate, and an adhesive described above forencapsulating the OED. Here, a first region of the adhesive covers theOED.

According to the present invention, the OED may be an organic lightemitting diode (OLED).

The encapsulated OED product may further include a passivation filmformed between the adhesive and the OED for protecting the OED.

Still another exemplary embodiment of the present invention is directedto providing a method of encapsulating an OED including applying anadhesive to a substrate having the OED formed thereon so that a firstregion of the adhesive may cover the OED; and curing the adhesive.

An operation of applying the adhesive to the OED may be performed bysubjecting the adhesive film to a hot-roll lamination, hot press orvacuum press method, but the present invention is not particularlylimited thereto.

The operation of applying the adhesive to the OED may be performed at atemperature of 50° C. to 90° C., and the curing may be performed byheating the adhesive at a temperature of 70° C. to 110° C. orirradiating the adhesive with UV rays.

Also, the method of encapsulating an OED may further include attaching asecond region of the adhesive to an additional encapsulation materialsuch as a glass or a metal so that the second region and theencapsulation material can come in contact with each other.

FIG. 4 is a cross-sectional view of an encapsulated OED productaccording to one exemplary embodiment of the present invention.

In the method of encapsulating an OED according to the presentinvention, for example, a transparent electrode is formed on a substrate21 such as a glass or polymer film using a method such as vacuumdeposition or sputtering, and an organic layer is formed on thetransparent electrode. The organic layer may include a hole injectionlayer, a hole transfer layer, a light emitting layer, an electroninjection layer and/or an electron transfer layer. Next, a secondelectrode is further formed on the organic layer. Thereafter, theabove-described adhesive 22 is applied onto the OED 25 formed on thesubstrate 21 so that the adhesive 22 can cover the entire organicelectronic device 25. In this case, a method of applying the adhesive 22is not particularly limited. For example, a cover substrate (e.g., aglass or polymer film) 24 to which the adhesive of the adhesive filmaccording to the present invention has been previously transferred maybe applied onto the OED 25 formed on the substrate 21 using a methodsuch as heating or compression. In this operation, for example, when theadhesive 22 is transferred onto the cover substrate 24, theabove-described adhesive according to the present invention may betransferred onto the cover substrate 24 using a vacuum press or vacuumlaminator while the base film or release film formed on the adhesive ispeeled off and heated. In this procedure, when the curing of theadhesive is carried out to an extent exceeding a certain range, theclose adhesion and adhesive strength of the adhesive 22 may be degraded.Thus, it is desirable to control a process temperature and a processingtime to approximately 100° C. or lower and 5 minutes, respectively.Similarly, when the cover substrate 24 to which the adhesive 22 istransferred is thermally compressed to the OED, a vacuum press or vacuumlaminator may be used. In this operation, the temperature condition maybe set as described above, and the processing time may be set to lessthan 10 minutes. However, the adhesive is applied to the OED so that theadhesive of the first region rather than the second region of theadhesive can come in contact with the OED (in contact with a passivationfilm when the OED includes the passivation film).

According to the present invention, the adhesive to which the OED iscompressed may also be further subjected to a curing process. In thiscase, the curing process (the inventive curing) may be, for example,performed in a heating chamber or a UV chamber. The conditions in theinventive curing may be properly selected in consideration of thestability of the OED.

However, the above-described manufacturing process is merely oneexemplary embodiment for encapsulating the OED according to the presentinvention. Thus, the process sequence and process conditions may beeasily changed. For example, the sequence of the transfer andcompressing process may be changed in the present invention in such amanner that the adhesive 22 according to the present invention is firsttransferred onto the OED 25 formed on the substrate 21 and the coversubstrate 24 is compressed. Also, when a passivation layer is formed onthe OED 25, the adhesive 22 may be applied to the passivation layer, andcured without forming the cover substrate 24.

EXAMPLE 1

1. Preparation of Solution for First Region

200 g of a silane-modified epoxy resin (KSR-177, Kukdo Chemical Co.,Ltd.) and 150 g of a phenoxy resin (YP-50, Tohto Kasei Co. Ltd.) wereput into a reactor, and diluted with MEK. Thereafter, the inside of thereactor was replaced with nitrogen, and the resulting solution washomogenized.

2. Preparation of solution for second region

70 g of CaO (Aldrich) was added as a moisture absorbent at aconcentration of 30% by weight to MEK to prepare a moisture absorbentsolution, and the moisture absorbent solution was milled for 24 hoursusing a ball mill process. Also, as a separate process, 200 g of asilane-modified epoxy resin (KSR-177, Kukdo Chemical Co., Ltd.) and 150g of a phenoxy resin (YP-50, Tohto Kasei Co., Ltd.) were put into areactor at room temperature, and diluted with MEK. Thereafter, theinside of the reactor was replaced with nitrogen, and the resultingsolution was homogenized. The moisture absorbent solution as previouslyprepared above was added to the homogenized solution, and 4 g of acuring agent, imidazole (Shikoku Chemicals Corporation), was added, andstirred at a high speed for 1 hour to prepare a solution for a secondregion.

3. Preparation of Adhesive Film

The solution for a first region as previously prepared above was appliedto a released surface of a release PET film using a comma coater, anddried at 130° C. for 3 minutes in an oven to form an adhesive layerhaving a thickness of 15 μm.

The solution for a second region as previously prepared above wasapplied to a released surface of a release PET film using a commacoater, and dried at 130 ° C. for 3 minutes in an oven to form anadhesive layer having a thickness of 30 μm.

The adhesive layers of the first and second regions were joined togetherto manufacture a multilayer adhesive film.

EXAMPLE 2

An adhesive film having a multilayer structure was manufactured in thesame manner as in Example 1, except that 7 g of CaO was added to thefirst region solution and 62 g of CaO was added to the second regionsolution in the manufacture of the adhesive film of Example 1.

EXAMPLE 3

An adhesive film having a multilayer structure was manufactured in thesame manner as in Example 1, except that 14 g of CaO was added to thefirst region solution and 56 g of CaO was added to the second regionsolution in the manufacture of the adhesive film of Example 1.

COMPARATIVE EXAMPLE 1

An adhesive film having a thickness of 45 μm was manufactured in thesame manner as in the manufacture of the adhesive film of Example 1,except that only compositions of the first region solution prepared inExample 1 were used.

COMPARATIVE EXAMPLE 2

An adhesive film having a thickness of 45 μm was manufactured in thesame manner as in the manufacture of the adhesive film of Example 1,except that only compositions of the second region solution prepared inExample 1 were used.

COMPARATIVE EXAMPLE 3

An adhesive film having a multilayer structure was manufactured in thesame manner as in Example 1, except that 28 g of CaO was added to thefirst region solution and 42 g of CaO was added to the second regionsolution in the manufacture of the adhesive film of Example 1.

EXPERIMENTAL EXAMPLE 1 Confirmation of Moisture Barrier Property

In order to examine the barrier properties of the adhesive filmsmanufactured in Examples 1 to 3 and Comparative Examples 1 to 3, acalcium test was carried out. More particularly, calcium (Ca) wasdeposited on a glass substrate having a size of 100 mm×100 mm to form 9spots with a size of 5 mm×5 mm and a thickness of 100 nm, and a coverglass to which each of the adhesive films of Examples 1 to 3 andComparative Examples 1 to 3 was transferred was heated at eachcalcium-deposited spot at 80° C. for 1 minute using a vacuum pressmethod. Then, each of the adhesive films was cured at 100° C. for 3hours in a high-temperature oven, and the encapsulated Ca test samplewas then cut into pieces with a size of 11 mm×11 mm The obtained testsamples were kept under conditions of a temperature of 85° C. and 85%R.H. in a constant temperature and humidity chamber, and a time pointwhere a Ca-containing coating solution started to show transparency dueto an oxidation reaction with penetrating moisture was determined. Theresults are listed in the following Table 1.

TABLE 1 Examples Comparative Examples Items 1 2 3 1 2 3 Time at which<240 <250 <270 <40 <230 <250 transparency is shown (hours)

EXPERIMENTAL EXAMPLE 2 Confirmation of Physical Damage

The adhesive films of Examples 1 to 3 and Comparative Examples 1 to 3were used to manufacture 3-inch organic light emitting panels. Then, theorganic light emitting panels were kept under the conditions of atemperature of 85° C. and 85% R.H. in a constant temperature andhumidity chamber, and damage to the organic deposited films wasobserved. The results are listed in the following Table 3.

TABLE 3 Items Film damage Example 1 No damage Example 2 No damageExample 3 No damage Comparative Example 1 No damage Comparative Example2 Organic deposited films are broken in the interface between amoisture-permeable region and a moisture-impermeable region ComparativeExample 3 Adhesive failure occurs

EXPERIMENTAL EXAMPLE 4 Confirmation of Chemical Damage

Silicon nitride (SiNx) used for a passivation film in the OED wasdeposited on a glass to a thickness of 1 μm. Each of the adhesive filmsof Examples 1 to 3 and Comparative Examples 1 to 3 was thermallycompressed onto the SiNx-deposited film, cured, and kept under theconditions of a temperature of 85° C. and 85% R.H. Thereafter, achemical change in the SiNx deposited film was analyzed using a Fouriertransform infrared (FT-IR) spectroscope. The results are listed in thefollowing Table 4, and the FT-IR analysis results on the adhesive filmsof Example 1 and Comparative Example 2 are shown in FIGS. 6 and 7.Unlike FIG. 6, it was analyzed that a change in chemical components ofthe SiNx-deposited film took place as shown in FIG. 7. Thus, it wasconfirmed that the chemical damage to the passivation film (theSiNx-deposited film) took place since a moisture-reactive absorbentserved as a strong alkali due to hydration.

TABLE 4 Film damage Example 1 No damage Example 2 No damage Example 3 Nodamage Comparative Example 1 No damage Comparative Example 2 Passivationfilm is chemically damaged Comparative Example 3 Passivation film ischemically damaged upon exposure to extreme environments

As described above, it could be confirmed that the adhesive films ofExamples 1 to 3 according to the exemplary embodiments of the presentinvention may serve to effectively encapsulate the OED from moisture,but effective encapsulation of the OED is not attained when the firstand second regions are not demarcated in the adhesive film or at least acertain content of the moisture absorbent is included in the firstregion.

The adhesive film according to the present invention may be useful ineffectively preventing moisture or oxygen flowing in the OED frompenetrating from the outside and also improving the lifespan anddurability of the OED.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. An adhesive for encapsulating an organic electronic device (OED), comprising: a curable resin, and a moisture absorbent, wherein the adhesive comprises a first region coming in contact with the organic electronic device (OED); and a second region not coming in contact with the organic electronic device (OED), wherein the moisture absorbent is present at contents of 0 to 20% and 80 to 100% in the first and second regions, respectively, based on the total weight of the moisture absorbent in the adhesive, and wherein the second region has a thickness of 5 μm to 200 μm.
 2. The adhesive of claim 1, wherein the adhesive has a viscosity at room temperature of 10⁶ dyne·s/cm² or more.
 3. The adhesive of claim 1, wherein the curable resin has a water vapor transmission rate (WVTR) of 50 g/m²·day or less when measured in a cured state.
 4. The adhesive of claim 1, wherein the curable resin is a thermosetting resin, a photocurable resin or a dual curable resin.
 5. The adhesive of claim 1, wherein the curable resin contains at least one curable functional group selected from the group consisting of a glycidyl group, an isocyanate group, a hydroxyl group, a carboxyl group, an amide group, an epoxide group, a cyclic ether group, a sulfide group, an acetal group and a lactone group.
 6. The adhesive of claim 1, wherein the curable resin is an epoxy resin having a ring structure in the molecular structure.
 7. The adhesive of claim 1, wherein the curable resin is a silane-modified epoxy resin.
 8. The adhesive of claim 1, wherein the moisture absorbent is a moisture-reactive absorbent, a physical absorbent, or a mixture thereof.
 9. The adhesive of claim 8, wherein the moisture-reactive absorbent is selected from the group consisting of alumina, metal oxide, metal salt and phosphorus pentoxide, and the physical absorbent is selected from the group consisting of silica, zeolite, zirconia, titania and montmorillonite.
 10. The adhesive of claim 9, wherein the moisture-reactive absorbent is at least one selected from the group consisting of P₁O₅, Li₂O, Na₂O, BaO, CaO, MgO, Li₂SO₄, Na₂SO₄, CaSO₄, MgSO₄, CoSO₄, Ga₂(SO₄)₃, Ti(SO₄)₂, NiSO₄, CaCl₂, MgCl₂, SrCl₂, YCl₃, CuCl₂, CsF, TaF₅, NbF₅, LiBr, CaBr₂, CeBr₃, SeBr₄, VBr₃, MgBr₂, BaI₂, MgI₂, Ba(ClO₄)₂ and Mg(ClO₄)₂.
 11. The adhesive of claim 1, wherein the second region of the adhesive comprises 1 to 100 parts by weight of the moisture absorbent, based on 100 parts by weight of the curable resin.
 12. The adhesive of claim 1, wherein the first region of the adhesive comprises 0 to 20 parts by weight of the moisture absorbent, based on 100 parts by weight of the curable resin.
 13. The adhesive of claim 1, wherein the adhesive further comprises a filler.
 14. The adhesive of claim 13, wherein the filler is at least one selected from the group consisting of clay, talc and acicular silica.
 15. The adhesive of claim 13, wherein the adhesive comprises 1 to 50 parts by weight of the filler, based on 100 parts by weight of the curable resin.
 16. The adhesive of claim 1, wherein the adhesive further comprises a curing agent.
 17. The adhesive of claim 16, wherein the curing agent is selected from the group consisting of an amine-based compound, an imidazole-based compound, a phenol-based compound, a phosphorus-based compound and an acid anhydride-based compound.
 18. The adhesive of claim 16, wherein the adhesive comprises 1 to 10 parts by weight of the curing agent, based on 100 parts by weight of the curable resin.
 19. The adhesive of claim 1, wherein the adhesive further comprises a high molecular weight resin comprising a phenoxy resin, an acrylate resin, an epoxy resin, a rugger or a reactive rubber.
 20. The adhesive of claim 1, wherein the first region has a smaller thickness than the second region.
 21. The adhesive of claim 1, wherein the first region and the second region is an adhesive layer.
 22. An encapsulated organic electronic device (OED) product, comprising: a substrate; an OED formed on the substrate; and the adhesive defined in claim 1 for encapsulating the organic electronic device (OED), wherein the first region of the adhesive covers the organic electronic device (OED).
 23. The product of claim 22, wherein the organic electronic device is an organic light emitting diode (OLED).
 24. The product of claim 22, wherein the organic electronic device (OED) comprises a passivation layer.
 25. A method of encapsulating an organic electronic device (OED), comprising: applying the adhesive defined in claim 1 to a substrate having the organic electronic device (OED) formed thereon so that the first region of the adhesive covers the organic electronic device (OED); and curing the adhesive.
 26. The method of claim 25, wherein the application of the adhesive to the organic electronic device is performed by subjecting the adhesive to a hot-roll lamination, hot press or vacuum press method.
 27. The method of claim 25, wherein the application of the adhesive to the organic electronic device is performed at a temperature of 50 to 90° C.
 28. The method of claim 25, wherein the curing of the adhesive is performed by heating the adhesive in a temperature range of 70 to 110° C. or irradiating the adhesive with UV rays.
 29. The method of claim 25, wherein the organic electronic device (OED) comprises a passivation layer.
 30. The adhesive of claim 1, wherein the organic electronic device (OED) comprises a passivation layer.
 31. An adhesive for encapsulating an organic electronic device (OED), comprising: a curable resin, and a moisture absorbent, wherein the adhesive comprises a first region coming in contact with the organic electronic device (OED); and a second region not coming in contact with the organic electronic device (OED), wherein the moisture absorbent is present at contents of 0 to 20% and 80 to 100% in the first and second regions, respectively, based on the total weight of the moisture absorbent in the adhesive, and wherein the adhesive has a viscosity at room temperature of 10⁶ dyne·s/cm² or more.
 32. An adhesive for encapsulating an organic electronic device (OED), comprising: a curable resin, a high molecular weight resin comprising a phenoxy resin, an acrylate resin, an epoxy resin, a rubber or a reactive rubber, and a moisture absorbent, wherein the adhesive comprises a first region coming in contact with the organic electronic device (OED); and a second region not coming in contact with the organic electronic device (OED), and wherein the moisture absorbent is present at contents of 0 to 20% and 80 to 100% in the first and second regions, respectively, based on the total weight of the moisture absorbent in the adhesive. 